The Small Cell technology uses low-power radio access nodes, and may be used to extend the coverage range of a Macro Cell to offload growing data flow of the Macro Cell and increase the utility efficiency of radio spectrum resources. Currently, the LTE-Advanced system uses the Small Cell technology to improve the network capacity.
Typically, the Small Cell has a small size, and its coverage range is between 10 meters to 2 kilometers. The deployment scenario of the Small Cell of the LTE network is more flexible, for example, the Small Cell deployment scenario in the LET network may include two levels: the Macro Cell and Small Cell, herein, the Macro Cell and the Small Cell may be deployed at the same frequency point, that is, co-channel deployment; or they may be deployed at different frequency points, that is, non-co-channel deployment. The Macro Cell may not be deployed, and only the Small Cell is deployed in the deployment scenario of the Small Cell of the LTE network. In addition, the Small Cell may be deployed in indoor environments, and may also be deployed in outdoor environments, and it may be deployed sparsely or densely.
The Small Cell is an interference-limited system, and there are complex interference relationships between the Macro Cell and Small Cell, as well as between the Small Cell and the Small Cell. Each cell dynamically schedules to serve terminals within the cell respectively. In addition, as the user equipment UE moves, there are UE continuously moving in and moving out of the Small Cell, the load and interference of the Small Cell system will show a significant fluctuation. Therefore, a certain interference coordination method must be adopted to inhibit and coordinate the interference in the Small Cell. For example, Small Cell adaptive switching mechanism and adaptive power adjustment mechanism.
Herein, the basic concept of the Small Cell adaptive switching mechanism is to adaptively open or close some Small Cells with very low load to reduce inter-cell interference. An opened cell is called an activated cell, and the activated cell normally transmits data channels and common channels. A closed cell is called a dormant cell, and the dormant cell closes data channels and some of common channels. However, both the activated cell and the dormant cell may transmit the cell Discovery Signal DS that is used for the cell discovery and selection, activation/deactivation judgment, and so on.
Currently, the existing reference signal, for example, Channel State Information Reference Signal CSI-RS, is taken typically as the DS resource. However, the function of the existing CSI-RS itself is configured for realizing CSI measurement, so that both a time-domain density and a number of antennas are relatively large. For the deployment scenario of the Small Cell, it is needed to measure more cells when the DS is being measured. Generally, a number of ports of CSI-RS transmitting antennas used for CSI measurement is relatively large, and a cycle is relatively short, and the DS doesn't need so many antenna ports or such short cycle. That is, if multiplexing directly the existing CSI-RS resource for the DS, it will undoubtedly cause a problem of unnecessary radio resource overheads.